In Hellenistic Greek this would be δὸς τῲ. The dative case has merged with the genitive case in modern Greek. Correct I am? (as Yoda would have said).

Indeed, but in both cases, τος was not yet a 3rd person pronoun. The earliest instance of it listed by Gignac's grammar of the papyri is A.D. 346. He also says Mayser found one example from the Ptolemaic papyri, but doesn't give a date for it.